A highly thermo-stable far-red LiMgAlF6:Cr3+ phosphor for plant-growth lighting

Abstract

The far-red light around 730 nm plays an important role during the plant growth. Herein, broadband far-red LiMgAlF6:Cr3+ phosphors were successfully prepared via the hydrothermal method. Under 424 nm excitation, LiMgAlF6:0.05Cr3+ exhibits an emission band peaking at 734 nm with a full-width at half maximum (FWHM) of 131 nm, due to the emission from two kinds of Cr3+. Moreover, the broad band could match well with the absorption spectrum of the plant's PFR. The phosphor not only owns a high internal quantum efficiency (IQE) of 45.6%, but also a good resistance towards to thermal quenching. Its emission intensity at 150 °C is 93.9% of the initial intensity at room temperature. Finally, the LiMgAlF6:Cr3+ powder was combined with a 460 nm blue chip to form one LED device, which was carried out on the growth of the tomato plants. The LED based on LiMgAlF6:Cr3+ can promote the growth of tomato plants, indicating the feasibility of phosphors for the plant-growth lighting.